This invention relates to certain new and useful improvements in two-wheeled hand trucks of the type wherein a primary frame, adapted in use to assume a generally vertically inclined position, and having a generally forwardly disposed load-supporting nose, is supported by the wheels, and at its upper end incorporates a handle portion which can be grasped by a user to propel the truck along. The frames of such hand trucks and of open framework configuration with side rail channels in opposing disposition receiving cross brace members which are spaced apart vertically along the frame. Trucks of this type are adapted to be used in the manual transport of various products of differing configuration which may, for example, comprise heavy rectangular boxes or cartons, or heavy barrels and kegs. When the truck is in use, the load is borne both by the nose and by the vertically inclined framework, and is in engagement with and imparts stresses to the cross rails. Hand trucks for transporting curvilinear products are normally provided with curved cross rails, but frequently owners of hand trucks with linear cross rails use them to transport heavy barrels, and of course, when they do, there is a line contact of the barrel with the cross rails. Dependent, therefore, on the products being handled, the cross rails are expected to bear a considerable load which may be spread over a substantial portion of the length of the cross rail, or may be centrally applied at a relatively limited load contact location.
In the past, cross rails have usually been formed of extruded metal in a generally tubular configuration as in U.S. Pat. No. 3,997,182. U.S. Pat. No. 4,235,449 discloses a cross brace or cross rail formed of plastic material, but also in a tubular configuration. While it is important that the cross rails have sufficient rigidity and strength to function as load-bearing members in shear, it is also important that they have torsional strength and stiffness, inasmuch as torsional stresses are applied to the hand truck during use at various times, for instance, as when a load is dumped sidewise off the hand truck, or when one wheel of the hand truck is up on a curb, and the other is moving to the pavement below.
Other important considerations in the manufacture of hand trucks is lightness and economy of manufacture, so that hand trucks can be made available to all the users who have need of them.
One of the prime objects of the present invention is to provide a hand truck with a tough, reliable cross brace structure which, when formed in channel shape, can incorporate internal ribs in a particular configuration which enhances the load bearing and load distributing characteristics of the member, both in shear and in torsion, and yet is extremely lightweight in character.
Still another object of the invention is to design a hand truck of the character described wherein the cross brace structure can be provided with tubular sockets which accommodate both the vertical package support rods which are utilized in some hand trucks, and the extensible handle frame portions which also are utilized in certain hand truck designs.
Another object of the invention is to design a hand truck construction of the character mentioned wherein curvilinear cross rails can be provided which are interchangeable to function in various positions, either to present flat or curvilinear faces to the load, depending on the nature of the particular loads expected to be transported on the hand truck.
Another object of the invention is to provide a hand truck construction of the character indicated, wherein the ends of the cross rails are received within channel-shaped side rails, and the cross rails are configured to facilitate the installation of fasteners in line with the longitudinal axis of the side rail, the ends being particularly designed to accommodate either a blind rivet fastener or the nut of a bolt and nut type fastener in a manner which permits preinstallation of the nut.